As electronic and optical devices and systems advance, they require greater power consumption, and thus, generate greater amounts of heat. Similarly, many energy conversion systems, such as fuel cells, batteries, power supplies, chemical and electrochemical energy storage, and many others, generate significant amounts of thermal energy as a result of their operation, which needs to be rejected to the environment. The problem of removing heat resulting from operation of devices and systems has grown from being an important concern to becoming a widely recognized bottleneck that limits further progress of high performance electronic, optical, and energy conversion and storage systems. Excessive heating affects not only the performance, but also the reliability of the components (e.g., computer chips) of the devices and systems. The heat generation from one component can causes performance and reliability problems for other components. Also, the heat generation can be general to a relatively large area and localized (“hot-spots”) to a specific component. Air cooling is a common method of cooling and can be used in conjunction with heat sinks providing an increased surface area for heat dissipation. Other heat transfer devices include heat exchangers, liquid cooling microchannel heat sinks, and heat pipes.
Advances are needed in heat dissipation devices to better meet the cooling needs of current and future electronic and optical devices and energy conversion systems. The major challenges arise due to significant spatial and temporal non-uniformity of heat generation (i.e., localized domains with transient spikes of high heat fluxes imbedded within large device plains of modest or no heat generation) as well as the limited space in vertical (perpendicular to the device plane) direction for deployment of extended surfaces (fins) for increasing the heat transfer area. Thus, to overcome these challenges, there is a need for cooling methods, devices, and structures that produce a very large heat transfer coefficient locally (e.g., employing phase change heat transfer) in combination with the ability for highly efficient lateral spreading of heat over a large distance to achieve a large heat transfer surface for eventual rejection of heat to the ambient using air cooling.
In summary, highly non-uniform heat generation, limited access to the place in the device where most of heat generation occurs, and the need for low weight and compact system design pose significant challenges to development of the cooling system.